The present invention relates to a catalyst containing the elements silicon, vanadium, sulphur and oxygen and at least one alkali metal element, a process for its preparation and its use in the oxidation of organic compounds with molecular oxygen.
Catalysts which contain the elements silicon, vanadium, sulphur and oxygen and at least one alkali metal are known in principle and are described, for example, in Fiat Report 649, London, 1947, page 2 to 3. According to this Report, they are prepared by treating potassium waterglass with sulphuric acid, drying the silicic acid thus obtained and subsequently impregnating it with a solution of a vanadyl compound, and subsequent shaping. The abovementioned publication furthermore discloses that the catalysts containing the elements silicon, vanadium, sulphur and oxygen and at least one alkali metal element can be used for the oxidation of naphthalene with molecular oxygen to give phthalic anhydride. In addition, Belgian Pat. No. 798,181 discloses that the catalysts containing the elements silicon, vanadium, sulphur and oxygen and an alkali metal can be employed for the oxidation of naphthalene with oxygen to give naphthoquinone.